Assigitob to wbstihg



Feb. 19, 1929.

F. B. FALKNOR RADIO TRANSMITTING SYSTEM Filed Jan. 29, 1927 Fig.1.

A Hormonic :6 Producer f 4 Receiving I 49 High Q Se+ 47 Speed n Recorder F 2 l 5 4 Receiving 5o 54 8 d 5| 8e+ v 55 pee /53 1 Recorder I High Speed Record Fig.5.

'ATTORNEY Patented Feb. 19, 192 9.

FRANK B. FALKNOIR, 0F WILKINSBURG, PENNSYLVANIA, ASSIGIIOB TO PATENT. oFFlcs.

VIESTING- HOUSE ELECTRIC &, MANUFACTURING COMPANY, A CQR-EORATIOII OF FEZINSYL- VANIA I RADIO TRANSMITTING SYSTEM.

Application filed January 29, 1927.

My invention relates to radio transmit-ting systems, and it has particular relation to systems of the type known as multiplex, in which a plurality of messages are simultaneously transmitted from a single radiating structure.

One object of my invention is to provide a system in which a plurality of materially different signalling frequencies may be superimposed upon the same carrier wave. Another object of my invention is to provide means for receiving the signals transmitted from a radio station constructed and arranged for multiplex signalling.

It has previously been proposed to accomplish the simultaneous transmission of a plurality of signals over a single carrier wave by modulating the intensity, or amplitude, of said wave at a. plurality of frequencies, utilizing each of such frequencies for a (if ferent signal. Systems of this type necessitate the use of complicated filter systems, both in transmission and reception. if interference between the various signals is to be completely eliminated.

By the present invention, therefore. instead of modulating the intensity, or amplitude, of a carrier wave at a plurality of frequencies, I proposeto maintain the amplitude constant, and to vary the frequency of the wave itself, as well as its continuity thus obviating the-necessity of complicated filter systems both in transmitting and receiving. I may utilize the frequency-shift for one of the signals, and the interruption of the carrier wave for another, the frequency of the carrier wave interrupt-ions being made so high that visual or audible reception of the signal represented by the frequency-shift is not interfered with.

Among the novel features which are con- Serial No. 16,67.

Fig. 2 is a diagrammatic view of a highspeed transmitting device.

Fig. 3 is a diagrammatic view of a receiving station equipped to receive multiplex signals.

Figs. 4 and 5 are views illustrating the forms which visible indications of multiplex signals may take in the event that t pe recorders are used. I

Referring specifically to Fig. 1 which illustrates a radio transmitting system of the so-called master-oscillator power-amplifier type, thermionic device 1 comprisinga filament 2, grid 3 and a plate l, has a movable electrode 5 connected to the grid tiereof that is associated with a piezo electric crystal 6. A fixed electrode 7 is conductively connected to the filament 2 and is arranged to. support the piezo electric crystal.

The winding of a relay 8 is associated with an armature 11 which carries the movable electrode 5, electric actuating current for the relay 8 being derived from a battery 12 under the control of a telegraph key 13.

An inductor 14 is connected between the plate 4 and the filament 2 through a source of plate potential 15, the inductor being shunted by a tuning condenser 16. The input circuit 17 of a harmonic producer 18 is inductively associated with the output inductor 14, the harmonic producer in turn being arranged to energize the input circuitof a power amplifier 21. The power amplifier has an output circuit comprising an inductor 22 and a tuning condenser 23.

The movable armature 2% of a sensitive relay device is conductively connected to the output inductor 22 of the power amplifier, and is operatively associated with a fixed contact element 26 which is conductively connected to a radiating structure 27.

The relay 25 is arranged to be supplied with actuating currentfrom a source 28, under the control of a movable member 31 so disposed as to normally rest upon a metallic cylinder 32 which is conductively connected to the power source.

A tape 33, of non-conducting material, such as paper. having perforations therein representing signals. is so arranged that it may be passed, ata high speed, between the movable member 31 and tie metallic cylinder 32, thus interrupting at signal frequency, the circuit between the source 28 and the relay 25. Motive power for the tape connected to a winding reel. I

Those portions of the apparatus which comprise the thermionic device 1, the piezo electric crystal 6, the telegraph key 13 and relay 8 and the harmonic producer 18 together co-operate to cause variations in the frequency supplied to the power amplifier, the variations in frequency being determined by the amount of .motion given to the movable electrode 5 by the actuating relay 8.

1 A preferred form of relay and crystalholding device is disclosed in the copending application of J. B. Coleman, Serial No. 127,725, filed August 7, 1926, and assigned .to the Westinghouse Electric & Manufacturing Company (Case 12514).

As explained in the aforesaid application of Coleman, the frequency generated by a crystal-controlled oscillator depends upon the relative spacing of the electrodes .asso ciated with the crystal. The apparatus may be so arranged that the spacing of the electrodes is varied between definite limits, one position of the electrodes corresponding to a signal interval and the other position of the electrodes corresponding to a spacing interval. Although the shift in frequency of the crystalcontrolled oscillator may be quite small, such shift ismagnifiedby the harmonic producer and gives rise to a shift of any desired number of cycles inthe ultimate output of the radio transmitting system.

By arranging theapparatus as illustrated, it is, therefore, possible to accomplish slowspeed signalling by altering the transmitting frequency at a rate corresponding to the manual operation of the telegraph key. i

The relay 25 which is arranged to be controlled by the mechanically moved tape '33,

causes an interruption in the continuity in the transmitted carrier wave, irrespective of its drawn into contact with the fixed contact member 26, and the power amplifier is accordingly condu'ctively connected to the ra dlating structure 27. Durlng intervals when the movable member 31 is separated from the of the contactand armature, thus interrupting the continuity of the carrier wave whenever the perforatlons 1n the tape 33 pernnt the movable member 31 to rest upon the cylinder 32. v

Referring specifically to Fig. ,3, the receiving structure may comprise an antenna 41, ,a non-inductive reactor 42, preferably .a resistor of high value, and a ground connection s3. Receiving apparatus 44, tuned to the frequency transmitted when the movable electrode 5 is at the upper limit of its travel, is connected to the resistor 42; This receiver has an output circuit which is com nected to a high-speed tape recorder 1-5 through conductors 46 and 47.

Areceiver 4E8, tuned to the frequency transmitted when the movable electrode 5 is at the other limit of its travel, is also operatively connected to the resistor42. I

This secondreceiver has an output circuit conductively connected to a low speed tape recorder 51 through conductors 52 and 53. The conductor 46 is connected to conductor 52 by means of a conductor 49, andfthe conductor a7 is connected to the conductor by a conductor 50. A plurality'of tuned rejcctor In order to explain the operation of a system constructed according to my invention, it is assumed that the'normal carrier frequency of the transmitter is of the'order of 25.000 cycles per second. The high-speed tape transmitter superimposes a signal on this can rier frequency by interrupting it at a speed. of approximately 400 letters per minute, or at even higher speeds.

The movable electrode!) is arranged to cause the crystaLcontrolled oscillator to shift in frequency a sufficient amount to change the carrier frequency from 25,000 cycles to 25,700'or 25,300 cycles, or togive the carrier any desired shift. The rate of shift of the signalling frequency should be at a low speed of approximately 100 or 200 letters per minute. r r 7 It is thus apparent that two distinctsignals may be superimposed upon the carrier 7 wave, one by interrupting its continuity ata high speed and the other by shifting its freof which frequency is being interrupted. To that end, I have provided the connections 49 I and 50 between the output circuits of the two tuned receivers, which connections enable the high-speed recorder l5 to give an uninterrupted indication of the signal being received at high speed by either of the said receivers. Inasmuch as the high-speed signal is conveyed by a series of interruptions in the transmitted frequency, it is obviously immaterial which of the two receivers is utilized to control the high-speed recorder.

In so far as the low-speed signals are concerned, the output of the receiver tuned to either of the limits to which the carrier wave is shifted is directly readable by ear, or may be recorded on a tape. The high-speed signal will exist in the low-speed record as a modulation which appears in both signalling and spacing intervals. If the difference between the speed of the interruptions to the carrier frequency and the speed at which the carrier is caused to shift in frequency be made sufficiently great, the modulation caused by the high-speed signal will not be objectionable nor will it interfere with the legibility of the tape recorded low-speed signal.

Referring to Fig. 4, the'high-speed record will be made substantially as shown, there being no interruptions to its continuity occasioned by the frequency shift of the carrier wave.

In Fig. 5 is reproduced a typical tape record such as is given by the low-speed re corder, and it will be noted that the highspeed signal appears therein merely as a roughness which in'no way interferes with -the legibility thereof.

Although I have shown and described a specific embodiment of my inventlon, I am aware that many modifications will be apparent'to those skilled in the art. My invention, therefore, is not to be limited except in so far as is necessitated by the prior art and by the spirit of the appended claims.

I claim as myinvention:

1. In a radio system, means for transmitting a signal by carrier-wave-frequency variations, means for simultaneously transmitting a second signal by interruptions of the carrier wave, and means for receiving and indicating both signals. 7

2. In a radiosystem, means for generating and radiating high-frequency oscillations, means for shifting the frequency of said oscillations to impress a signal thereon, means for simultaneously interrupting the continuity of said oscillations to impress another signal thereon, and means for simultaneously receiving and indicating both signals.

3. In a radio system, means including a master-oscillator for generating and radiating highfrequency oscillations, means for altering the frequency of said master-oscillator to impress a signal on said oscillations, means for simultaneously interrupting the continuity of said oscillations for impressing another signal thereon, and means for receiving and indicating both signals.

4. In a radio system, means including a piezoelectric-crystal controlled master-oscillator for generating and radiating high-fre quency oscillations, means for altering the oscillation frequency of said crystal to impress a signal on said oscillations, means for interrupting the continuity of said oscillations to impress another signal thereon, and means for simultaneously receiving and indicating both signals.

5. In a radio system, means for generating and radiating higlrfrequency oscillations, means for shifting the frequency of said oscillations between definite limits to impress a signal thereon, means for simultaneously interrupting the continuity of said oscillations to impress another signal thereon, a plurality of receiving means tuned respectively to said frequency limits, and indicating means under the joint control of said receiving means.

6. In a radio system, means for generating and radiating high-frequency oscillations, means for shifting the frequency of said oscillations between definite limits to impress a relatively low-speed signal thereon, means for interrupting the continuity of said oscillations at a relatively high speed to impress another signal thereon, a plurality of receiving means responsive respectively to said frequency limits, indicating means for said high speed signals under the joint control of said receiving means, and indicating means under th control of a single one of said receiving means for recording said frequency shifts.

7. In a radio system, means for generating and radiating high-frequency oscillations, means for shifting the frequency of said osillations to impress a signal thereon, and

means for simultaneously interrupting the continuity of said oscillations to impress a second signal thereon.

In testimony whereof, I have hereunto subscribed my name this 2Sth day of January, 1927.

FRANK B. FALKNOR. 

